1. Field of the Invention
The present invention relates to an apparatus for mixing solid particulate matter into a fluid flow and for dispensing the fluid-solid mixture therefrom. The apparatus is primarily intended for use in the application of pesticides by dusting.
2. Description of the Prior Art
Quite frequently, it is desirable to apply a substantially uniform coat of a powder-like material to an object. For example, in various manufacturing operations it is often desirable to apply a powdered resin coating to an article or a particular section of an article for subsequent curing so as to form a coating thereon. Yet other examples calling for the application of powdered dry material are readily observable in plant-related industries. It is for example, well known to apply pesticides, fungicides, fertilizers, and similar such materials to plants in both agricultural and ornamental environments. In recognition of these needs, numerous prior art devices have been developed and are known in the prior art for mixing a solid particulate matter with a fluid flow stream for ultimately dispensing the solid material onto a predetermined object or surface.
Perhaps one of the earliest teachings in the prior art is given by U.S. Pat. No. 56,558. That patent to Hendley teaches the use of a bellows having a sand reservoir disposed so as to dispense sand into the fluid flow stream exhaust from the bellows.
U.S. Pat. No. 2,126,924 to Rose discloses a spraying device particularly intended for use in powder-spraying foilage. The Rose device is, in construction and operation, virtually identical to a pump-type spraying for the mixing and dispensing of liquids. The liquid concentrate reservoir is, in Rose, replaced by a dust reservoir. However, it should be noted that the dust is injected into the fluid flow stream outside the device. This may result in uneven application of the powder. Furthermore, since the powder exit is outside the device, the exit's orifice is subjected to atmospheric conditions and may become blocked. This also provides a substantially unobstructed passageway for the admission of moisture into the powder reservoir.
Yet another dusting device is shown in U.S. Pat. No. Des. 180,095. Finally, a blower-operated powder dispenser is taught by U.S. Pat. No. 3,854,634 to Hart. That patent teaches a construction whereby the entire fluid flow from a blower is admitted into a powder reservoir. The reservoir contains a diffuser plate placed within the reservoir upstream of the powder. As the fluid flow passes around the diffuser plate particulate matter is mixed into the flow stream. Finally, an exit is provided for the ultimate dispensing of the fluid including the particulate matter dispersed therein.
While other examples of such powder dispensers are known in the prior art, it should also be noted that prior art teachings concerning fluid-fluid mixing and dispensing as well as fluid-gas mixing and dispensing apparatus may also be considered as pertinent to the subject matter of this invention. For example, U.S. Pat. No. 4,039,105 to Chan discloses a liquid-liquid mixing and dispensing device for the application of liquid fertilizer in combination with water delivered by an ordinary garden hose.
In light of these prior art teachings, and with particular regard to those devices concerning powder dispensing and dusting, certain unsolved problems are apparent. First, virtually all the prior art devices include a fixed reservoir for the powder material. In order to change the material being applied it is necessary to physically empty the reservoir. In some instances, depending upon the compatibility of the powder materials being utilized, extensive cleaning might also be required. Additionally, certain ones of the prior art devices are constructed so as to provide virtually unobstructed access from the powder to the atmosphere. Not only might this be dangerous, but also it will necessarily tend to enhance any hydroscopic characteristics of the material, resulting in caking of the material and, ultimately, unoperability of the device.
It is therefore apparent that there is a great need in the art for a fluid-solid mixing and dispensing apparatus including the means for easily and rapidly changing, or replacing, the solid material being mixed and dispensed therefrom. Of course, the container for the powdered material should, insofar is practical, be protected from the atmosphere so as to inhibit its absorption of moisture as well as to prevent the accidental discharge of powder from the device. As with any article of manufacture, the apparatus satisfying these needs should be of relatively simple construction and operation. On many occasions the solid material being mixed and dispensed will have corrosive tendencies. Accordingly, such an apparatus should be constructed so as to prevent the entry of particulate matter into the blower section of the device.